Precision studies of radioactive molecules relevant to fundamental physics

Certain molecules that contain heavy, deformed radioactive nuclei are predicted to be exceptionally sensitive laboratories to examine the fundamental symmetries of nature [1-4]. Despite their recognized potential, technical challenges prevented experimental studies of these systems until very recently. The first landmark study of a short-lived molecule was able to determine the rovibronic structure of different isotpologues of radium monofluoride [5,6] , a promising system in which to search for signatures of symmetry violations.

This contribution presents results from subsequent experimental campaigns in which a massive improvement in resolution enabled an unprecedented glimpse into the structure of the radioactive ^223,225,226RaF. This allowed the laser cooling scheme of ²²⁶RaF to be established which will be critical for realizing future high-precision studies. Furthermore, the hyperfine structure in ²²⁵RaF is shown to be highly sensitive to the Bohr-Weisskopf effect, laying the foundation for the first studies of the distribution of nuclear magnetization in a molecule. Additional results characterising a plethora of newly observed excited electronic states as well as an accurate determination of the molecule's ionization potential will also be presented.

[1] Altuntaş, E. et al., Phys. Rev. Lett. 120, 142501 (2018)

[2] ACME Collaboration, Nature 562, 355–360 (2018)

[3] Flambaum, V. V. et al., Phys. Rev. Lett. 113, 103003 (2014)

[4] Berger, R. et al., WIREs Comput. Mol. Sci. 9, e1396 (2019)

[5] Garcia Ruiz, R. F. et al., Nature 581 396–400 (2020)

[6] Udrescu, S. M. et al. Phys. Rev. Lett. 127 03301 (2021)